The present invention relates to stabilised bitumen emulsions and their incorporation into composite compositions comprising either hydraulic or organic binders, or inorganic fillers, or a mixture of these components. The present invention relates more particularly to surfactant-stabilised aqueous emulsions of bitumen, and compositions formulated from such emulsions and designed to be incorporated at the time of use into the above components, for use in the building industry or civil engineering, and notably mortar-adhesive compositions, seams for roads and highways, paints, mortars for flooring, coatings and concretes.
The formulation of mortar-adhesive type products, coatings for outer facings, paints, coatings for finishing floors, etc comprises a basic binder, generally hydraulic or organic, to which the various additives, or even other binders, are added, to improve, among other things, rheological properties (facilitating implementation), mechanical characteristics, and drying characteristics. Frequently, when hydraulic binders are used for example, polymers are incorporated for improving mechanical strength characteristics, flexibility, and ability to withstand deformation. In the case of hydraulic binders, this polymer is generally in the form of a polymer in emulsion or in dispersion (latex, for example). This additive represents a non-negligible supplementary cost in such formulations, which it is desirable to reduce.
The question of using bitumen in emulsion, known to be inexpensive, has frequently been posed, but great difficulties in achieving formulations in the fields of application applicant is aiming at were encountered, as:
a bitumen emulsion that is stable over a long period must be provided, notably stable for more than six months, before mixing it with products which are frequently in powder form, whether or not pre-formulated, in the dry state, meaning that the complete product should be able to be stored in the form of a kit of components;
the hydraulic binders or inorganic fillers of the formulation flocculate or cause the emulsion to flocculate during mixing therewith;
the formulations to be provided do not achieve the desired characteristics or the formulations are too complex or expensive to be employed in practice.
The applicant has consequently set out to obtain bitumen emulsions which can meet these objectives, having universal suitability for incorporation, without breaking the emulsion, into formulations, for example for construction, which are easy to implement, in other words, notably, not presenting problems of delaying or accelerating setting.
Bitumens are mixtures of heavy hydrocarbons, essentially naphthenic and paraffinic, originating from the distillation of crude oils. These products are distillation residues and are classified by their physical properties, their chemical properties varying very widely as a function of the origins of the crude. Generally speaking, conventional crudes contain up to 30% bitumen, and heavy crudes up to 50%. As bitumen requirements of the majority of countries represent 2 to 4% of their crude oil consumption, this means that bitumen is available in very plentiful supply. Bitumens contain such a diversity of constituents that it is impossible to define their exact composition; nevertheless, it is possible to classify these constituents into major chemical families:
saturated compounds, essentially paraffinic;
aromatic compounds, in which 30% of the carbon atoms are included in aromatic cycles, with a sulphur content of around 2 to 3%;
asphaltenes, which are insoluble in hydrocarbons, are aromatic and rich in sulphur, nitrogen, and oxygen; they take the form of black brittle solids practically incapable of being melted.
For given bitumens, the percentage of these various families depends heavily on the extraction method used. Thus, products of this type are essentially classified by the following physical properties: penetrability (NFT 66-004), softening point (NFT 66-008), density (NFT 66-007), flashpoint (NFT 60-118), solubility (NFT 66-012) ductility (NFT 66-006), brittleness point. Commercially available bitumens, classified by penetrability index, are generally situated between 10 and 200. Currently, only two grades are able to remain emulsified at atmospheric pressure, the 80/100s and 180/220s, but it is possible, in certain cases, to emulsify 40/50 grade.
Like all materials, bitumen is sensitive to fatigue, and consequently its breaking strength can fall when subject to repeated stresses. As against this, it has a self-repairing capability allowing the destructive effects of fatigue phenomena to be limited. It is known to improve the flexibility properties of some bitumens by mixing them with synthetic elastomers such as styrene-butadiene polymers or atactic polypropylene.
Bitumen emulsions were developed for making cold coating compounds, some 60 years ago, and numerous articles and patents disclose bitumen emulsions manufacture by associating several surfactants of different natures. The three main types of emulsion are:
cationic emulsions, in which the surfactants are constituted by polar molecules of formula RNH3+ Xxe2x88x92, R being the hydrocarbon chain constituting the lipophilic portion of the molecule, and NH3+ Xxe2x88x92 the hydrophilic portion, Xxe2x88x92 being any anion whatsoever of a strong acid.
anionic emulsions of general formula Rxe2x80x94Yxe2x80x94 C+, R being the hydrocarbon chain constituting the lipophilic portion, and Yxe2x88x92 C+ being the hydrophilic portion, Yxe2x88x92 being a carboxylic, sulphonic, sulphuric, phosphonic or phosphoric group, C+ being a metal cation, frequently alkaline, or ammonium;
non-ionic emulsions, in which the surfactants are constituted by molecules of the Rxe2x80x94(EO)nxe2x80x94OH type, in which R is the hydrocarbon chain constituting the lipophilic portion of the molecule, the hydrophilic portion being constituted by the xe2x80x94(EO)n xe2x80x94OH radical (EO signifying ethylene oxide). The most frequently encountered bitumen emulsions are however cationic or anionic emulsions.
The surfactants employed for obtaining these emulsions are chosen so as to stabilise the emulsion during the period of storage, which frequently is not very long, for example only a few weeks, in the case of emulsions for roads and highways for carrying out cold coating. Moreover, it is frequently necessary to add components other than surfactants such as thickeners, to improve their stability.
Generally speaking, bitumen emulsions are made hot, by mixing, continuously or discontinuously, the two pre-heated phases (water at 50xc2x0 C., bitumen from 140xc2x0 C. to 170xc2x0 C.) using a disperser, the emulsifying surfactant being able to be introduced previously into either the aqueous or bitumen phase. Examples of known emulsions obtained in this way are given below in table 1:
The bitumen emulsions thus obtained are used in many different ways. For example, in the road making field, it is known to xe2x80x9cprovoke breakagexe2x80x9d of the bitumen emulsion by introducing a small amount of a cement into it the sole effect of which is to cause the medium to flocculate and improve departure of water. These emulsions are, in effect, formulated so as to provoke their destabilisation in the presence of inorganic granulates or powers (e.g. silica, chalk, cement). The most common applications of these types of emulsions are bituminous beds or base courses, cold surfacing materials, bituminous slurries, and keying and waterproofing layers. Applications other than road making are essentially those of sealing compounds for dams and canals in civil engineering as well as roof and foundation waterproofing in the building industry.
Cationic surfactants, (like amphoteric surfactants) cannot be used where it is desired to mix the bitumen emulsions and a hydraulic binder, such as a cement, which is basic by nature, as, inevitably, the emulsion is broken in this case. Thus, the oxyethylated fatty amines, alkylimidazolines, and the alkyl betains, are for example surfactants that cannot be used for providing the emulsions according to the present invention.
The anionic surfactants, comprising carboxylates, sulfates, sulfonates, phosphates and phosphonates, are not suitable for producing bitumen emulsions intended to be mixed with a hydraulic binder. In particular, the phosphates and phosphonates lead to hydration modifications of the hydraulic binder and significant set retardation.
Known non-anionic surfactants employed in these emulsions offer a wide diversity of forms and chemical natures: one for example can distinguish fatty alcohols, alkylphenols, various vegetable oils, whether or not ethoxylated, and condensates of ethylene and propylene oxides.
Non-ionic bitumen emulsions are disclosed in French patent 2,246,509 and U.S. Pat. No. 5,156,652. U.S. Pat. No. 5,156,652 discloses a possible combination of non-ionic surfactants for stabilising a bitumen emulsion designed to be transported over great distances via pipelines. The surfactants disclosed are essentially ethoxylated alkylphenol, but the latter can be used in combination with an ethoxylated and propoxylated alcohol block copolymer, of the following formula:
(CH2xe2x80x94CH2xe2x80x94O)10-125xe2x80x94(CH2xe2x80x94CHCH3xe2x80x94O)25-30xe2x80x94(CH2xe2x80x94CH2xe2x80x94O)10-125xe2x80x94H
French Patent Application 2,246,509 discloses the use of non-ionic surfactants for stabilising asphalt emulsions, the surfactants being able to be ethoxylated alkylphenols in combination with polyethylene alkylethers of the following formula:
C8-C22.alkyl-Oxe2x80x94(CH2xe2x80x94CH2xe2x80x94O)8-80xe2x80x94H
Contrary to the prior art documents, this invention sets out to provide an aqueous bitumen emulsion, with a high bitumen concentration (50 to 70%), which is not only stable over a storage time which can exceed six months, but which can be incorporated into various formulations, for example comprising one or several inorganic or organic binders, and/or one or several inorganic or organic fillers, without causing flocculation, or breaking the emulsion, when the various constituents are being mixed, and without modifying setting or rheology of the mixture. The emulsions according to the invention are characterised by the fact that they have very great stability, thus facilitating their storage over several months, and during mixing with the other constituents of the formulation, for example with a hydraulic binder, the formulation remaining homogeneous and ready and quick to use, which gives the emulsions according to the invention a practically universal character, in terms of possible applications.
The bitumen emulsion thus constituted then provides mixtures into which it is incorporated with particular properties such as, for example, adhesion, flexibility, sealing properties, these properties having previously been obtained using polymers in dispersion or in the re-dispersible powder form.
The invention consequently provides an aqueous bitumen emulsion constituted by the following components, expressed as a percentage of total emulsion weight
50% to 70% bitumen;
0.5% to 10% surfactant;
from 0 to 5% thickener;
from 0 to 1% anti-foaming agent;
water to make up to 100%
the emulsion being characterised in that the surfactant is constituted by at least one surfactant selected from the group consisting of a copolymer of ethylene oxide and propylene oxide, of PO/EO ratio comprised between 1.5 and 10, an epoxydated, ethoxylated and/or propoxylated surfactant, and a polyvinyl alcohol of molecular weight comprised between 10,000 and 150,000.
In the description and claims of this invention, the term xe2x80x9cPO/EO ratioxe2x80x9d means the molar ratio of the PO/EO groups, i.e. the number of PO (propylene oxide) groups to the number of EO (ethylene oxide) groups.
Preferably, the molecular weight of the copolymer of ethylene oxide and propylene oxide is comprised between 1000 and 2200, and it is preferably 2000. For comparison, the molecular weight of the block copolymer disclosed in U.S. Pat. No. 5,156,652 is comprised between 2350 and 12,750.
The copolymers employed as a surfactant in bitumen emulsions according to the invention, and as defined previously, do not lead to foam formation during preparation of the emulsion, thereby facilitating preparation of the latter. Also, when emulsions containing these copolymers are used for preparing compositions containing a hydraulic binder, they cause neither retardation nor acceleration of setting of said binder.
Preferably, and in order to augment the effectiveness of the copolymer defined above, the emulsion can include a supplementary surfactant playing the role of a hydrotrope. Advantageously, the supplementary surfactant is selected from the group consisting of the following non-ionic surfactants:
polyethoxylated alkylphenols of HLB value comprised between 13 and 17, and in particular selected in the group consisting of nonyl phenols 10 EO to 20 EO and tributylphenol 11 EO to 30 EO;
polyethoxylated fatty alcohols of HLB value comprised between 12 and 15, for example, isotridecanol 8 EO, decanol 8 EO, tridecanol 10 EO, and dodecanol 7 EO.
Unexpectedly, applicant has discovered that the polyethoxylated alkylphenols of HLB value comprised between 13 and 17 give the best results. Consequently, and preferably, the supplementary surfactant is a polyethoxylated alkylphenol of HLB value comprised between 13 and 17.
The HLB (hydrophilic-lipophilic balance) can be calculated using Griffin""s formula below:
HLB=20xc3x97m EO/m T
in which EO represents the total ethylene oxide weight and m T the total weight of the molecule.
All the non-ionic surfactants mentioned previously additionally have the advantage of only slightly influencing the hydration characteristics of cements, when emulsions containing these surfactants are employed for formulating this type of composition.
In one preferred embodiment, the surfactant of the bituminous emulsion is a mixture of a copolymer constituted by an ethylene oxide and propylene oxide copolymer of PO/EO ratio comprised between 1.5 and 10 and having a molecular weight of 2000, and of a nonylphenol 10 EO to 20 EO.
In this case, and preferably, the percentages of the surfactant constituted by the ethylene oxide and propylene oxide copolymer, as previously defined, mixed with nonylphenol 10 EO to 20 EO, are from 0.7% to 5% and from 0.1% to 1% respectively. Indeed this binary mixture of two non-ionic surfactants has proved to be the most effective for achieving stable bitumen emulsions, designed for mixing with hydraulic binders.
Despite the low surfactant concentration needed to obtain stability of the emulsion (around 0.5% by weight), it has proved to be important to use higher concentrations in mortar compositions, in order to avoid them flocculating. Indeed, when emulsions according to the invention are employed in mortar compositions, it is preferred to use at least 3% copolymer in the emulsion, with a copolymer/supplementary non-ionic surfactant ratio comprised between 5 and 7.
The invention further provides a method for producing an aqueous emulsion of bitumen as previously defined, characterized in that it comprises the steps consisting of:
preparing an aqueous phase, preferably using a thickener incorporated into water with stirring;
adding to said aqueous phase, a surfactant constituted by at least one surfactant chosen from the group consisting of an ethylene oxide and propylene oxide copolymer in a PO/EO ratio comprised between 1.5 and 10, an epoxydated ethoxylated and/or propoxylated surfactant, and a polyvinyl alcohol of molecular weight comprised between 10,000 and 150,000;
heating the aqueous phase to about 60xc2x0 C.;
incorporating the bitumen, previously heated between 140xc2x0 C. and 180xc2x0 C., into the aqueous phase under powerful mechanical stirring.
An anti-foaming agent can be employed before, during or after incorporating the bitumen phase if foaming occurs.
The invention further provides a composition based on at least one hydraulic or organic binder, and/or based on at least one inorganic or organic filler, containing a bitumen emulsion as defined above.
The invention also covers the use of an aqueous bitumen emulsion for formulating a composition selected in the group consisting of mortars, mortar-adhesives, coatings for facings, finishing coatings, paints, concretes, keying primers, waterproofing primers, roadway seams, and sealing mortars, the emulsion comprising, expressed as a percentage of total emulsion weight:
50% to 70% bitumen;
0.5% to 10% surfactant
water to make up to 100%,
said surfactant being constituted by at least one non-ionic surfactant selected from the group consisting of:
polyethoxylated alkylphenols of HLB value comprised between 13 and 17;
copolymers of EO and PO;
polyethoxylated fatty alcohols of HLB value comprised between 12 and 15;
epoxydated ethoxylated and/or propoxylated surfactants;
and polyvinyl alcohols of molecular weight comprised between 10,000 and 150,000.
Finally, the invention also provides a constructional materials kit, comprising, firstly, the bitumen emulsion as defined or used previously or obtained by the method described previously, and, secondly, at least one hydraulic or organic binder, and/or at least one inorganic or organic filler.
Preferably, the bitumen is selected from bitumens emulsifiable at atmospheric pressure, such as the 40 to 220 penetrability index grades (some tenths of a millimetre penetration). Deasphaltated or synthetic grades, as well as mixtures plastified using polymers can also be employed for particular applications, the grades from synthesis being useful in view of the possibility of pigmenting them.
The thickeners are preferably chosen from polysaccharides such as cellulosic thickeners, vegetable gums (for example, carob gum, guar gum, gum tragacanth, karaya gum, starch, alginates, gum arabic), gums produced by bacterial fermentation (for example xanthane gum, welan gum), and expanded clays, (for example attapulgite, sepiolite, bentonite). Other thickeners of the synthetic type can optionally be used for adjusting suspension rheology such as associative or non-associative acrylic polymers and polyurethanes. Welan gum has proved not to lead to substantial foam formation, unlike other gums, and for this reason it is the preferred thickener for the emulsions according to the present invention.
An anti-foaming agent can optionally be incorporated in the emulsion for avoiding foam formation and facilitating the incorporation of the bitumen. The anti-foaming agents are selected from products known to the skilled person such as, for example, mixtures of silica and mineral oil, polysiloxanes, tributylphosphate, and metallic soaps.
Preferably, the hydraulic binder is constituted by at least one hydraulic binder selected from the group consisting of a Portland cement or equivalent, high-alumina cement and a calcium sulphate.
In one preferred embodiment, the organic binder consists of at least one polymer binder, chosen from the group consisting of butadiene styrenes, acrylic copolymers, and ethylene polyvinylacetates.
Preferably, the mineral filler consists of at least one generally inert filler of the type habitually used in formulations for the building and civil engineering industries, chosen from the group consisting of sand, aggregates, silica, calcium carbonate, calcium silicates, barium sulfates, talc, mica.
Preferably, the organic filler consists of at least one organic filler chosen from the group consisting of polymer fibers, cellulose fibers, and/or polystyrene balls.